Electric arrester



P. BENDMANN.

ELECTRIC ARRESTER. APPLICATION FILED APR-1,1921.

Patente Apr. 18 1922.

UNITED STATES PATENT OFFICE.

PETER BENDMANN, 0F FRANKFORT-ON-THE-MAIN, GERMANY.

ELECTRIC ARRESTER.

Application filed April 1,

T 0 all whom, it may con-00m:

Be it known that 1, PETER BENDMANN, a German subject, and resident of Frankforton-the-Main. Germany, have invented new and useful Improvements in Electric Arresters, (for which I have filed application in Germany August 9, 1919, No. 390,329,) of which the following is a specification.

Excess voltage arresters are known that comprise a spark gap, which can be short circuited by a magnetically controlled switch for the purpose of discharging the excess voltage to earth. These excess voltage arresters have hitherto only been used for di-' rect current or for single phase alternating current. The present invention relates to an excess voltage arrester for polyphase alternating currents. t It is so arranged that all the phases are simultaneously shunted when one or more phases operate so that all phases are earthed and are also simultaneously short circuited with one another. The shunting and short circuiting is effected by means of a single electro-magnetically controlled switch, which, after discharging the excess voltage, automatically again disconnects the earthed lead. The apparatus is so arranged that there is a resistance behind the spark gap and the winding of the electromagnet of the switch is connected in parallel with this resistance. This arrangement enables all excess voltages exceeding about 10% of the normal to be discharged with reliability. The apparatus operates so quickly that the are at the discharge point'cannot cause any damage to the insulators, etc.

The accompanying drawing shows diagrammatically by way of example such an excess voltage switch. A transformer a is connected to a line I) comprisin three wires corresponding to three phases. ranched off from this line are the three spark gaps c, hehind which, over a common resistance (Z, a conductor 6 is connected to earth. The resistance (Z is short circuited by the coil 7 of the electromagnet, which operates a switch it pivoted at 9. Branch conductors 2' lead from spark gaps c to the contacts of this switch.

In front of these branch conductors 2' there are resistances is inserted in the individual ccnductors.

' @n the occurrence of an excess voltage in any of the phases, there is a spark discharge at the corresponding spark gap 0. Since resistance a3 is greater than coil the greater of the capacity current or the supply Specification of Letters Patent.

Patented Apr. 18, 1922.

1921. Serial No. 457,778.

current following the spark discharge goes through this coil f, which is thereby energized and pulls up the switch arm la. There- 'by all the spark gaps are connected to the earthed lead 6 and are short circuited with one another. Hence the discharge are at the spark gap is extinguished and no more current passes through the coil f; thus the switch h is released and disconnects the earth conductor from the branch leads 2'. Preferably, an oil immersed switch should be used.

The apparatus operates in a very similar manner during momentary earthing of the overhead line or when one of its insulators breaks down. Thereby one phase is con nected to earth and an excess voltage occurs at the spark gaps of the other phases of the excess voltage arrester so that these cause the apparatus to operate.

The current in the are at the overhead line can now flow away over the excess voltage arrester since its resistance is less than that of the arc, thereby the disturbance is re moved and the contact is again opened.

Now what I claim and desire to secure by Letters Patent is the following:

1. In excess voltage arresters for polyphase alternating current lines, a permanently maintained spark gap for each phase, a switch for grounding said gaps and electro-magnet mechanism for closing said switch when current passes any one of said gaps, said switch automatically returning to normal position upon the cessation of current through said mechanism.

2. In an excess voltage arrester i'or poly phase alternating currents, comprising spark gaps on each phase a'switch to short circuit phases. a resistance, switch in parallel with said grounded resis 3. In an excess voltage arm for polyphase alternating currents, cnnprising a branch from each phase conductor, having a permanently maintained spark ground connection for said branches. a. switch, an operating coil "for said switch hetween the gaps and ground and a. resist nce in parallel with coil. said grounded switch automatically short circuiting said branches upon the passage oi current a gap automatically returning to normal pQS'iii-lOIF. upon cessation of current aero 4:. Tn an excess voltage aria L r p phase alternatingcurrents, branch from each phase coeds ground connection common thereto, a spark gap in each branch and a resistance between each spark gap and the phase conductor, a switch point connected to each branch be tween the spark gap and resistance, a switch common to all of said points, a resistance in said ground connection and a switch operating solenoid in parallel with said last named resistance whereby said grounded switch 10 short circuits and grounds said branches 

